Jorge Marquet

Metal complexes in organic synthesis. : Preparation of α-(l-adamantyl)-β-dicarbonyl compounds and 4-(1-adamantyl)-3,5-disubstituted pyrazoles and isoxazoles

Abstract α-(1-Adamantyl)-β-dicarbonyl compounds are prepared by the reactions of the Co(II) complexes of β-dicarbonyl compounds with 1-bromoadamantane. This provides a route to the previously inaccessible 4-(1-adamantyl)-3.5-disubstituted pyrazoles and isoxazoles.

Copper and cobalt mediated regioselective alkylation of polyketide models: methyl 3,5-dioxohexanoate and triacetic acid lactone

Abstract Regioselective C-alkylations at the intercarbonyl positions C-4 and C-2 of the polyketide model methyl 3,5-dioxohexanoate, 1 , have been acomplished through reactions of its cobalt(II), 4a , and copper(II), 4b , complexes respectively. Some examples of double alkylations at both positions are presented. Cyclizations of the regioselectively substituted diketoesters so prepared gave triacetic acid lactone derivatives regioselectively alkylated at C-5 and at C-3.

On the regioselectivity of the nucleophilic aromatic photosubstitutions of 4-nitroveratrole. A threefold mechanistic pathway

Abstract 4-Nitroveratrole (NVT) is photosubstituted with primary amines, piperidine and hydroxide ion. Primary amines and hydroxide ion cause replacement of the methoxy group in meta position with respect to the nitro group whereas piperidine photosubstitutes the methoxy group in para to the nitro group. Photoreactions with piperidine and hydroxide ion involve attack of the amine upon a triplet excited state of NVT.Mechanistic evidences indicate that the reaction with hydroxide ion is probably a S N 2 3 Ar * process whereas the reaction with piperidine involves a radical ion pair formed via electron transfer from the amine to a triplet excited state. Photoreactions. with primary amines involve attack of the amine upon a singlet excited state of NVT (S N 2 1 Ar * process). These results are discussed and justified in the context of nucleophile ionization potential considerations and ground state donor-acceptor complex formation abilities.

The nucleophilic aromatic photosubstitutions of 4,5-dinitroveratrole with amines. Photoreductions of aromatic dinitrocompounds

Abstract 4,5-Dinitroveratrole is effectively photosubstituted by amines with relatively high ionization potential such as methylamine, n-butylamine and ethyl glycinate, but is mainly photoreduced when amines with relatively low ionization potential, such as dimethyl or trimethylamine are used. The photoreduction of several aromatic dinitrocompounds by triethylamine gives nitroanilines. A mechanistic scheme is proposed embracing our photosubstitutions and photoreductions, based on our experimental results and on MINDO/3 calculations of the ground states and the more likely intermediates.

Alkylation of β-diketones through their co(II), co(III) and zn(II) complexes. 1-Bromoadamantane as alkylating agent.

Abstract α-(1-adamantyl)-β-diketones are now accessible by the alkylation of Co(II) complexes of β-diketones with 1-bromoadamantane. The intermediacy of adamantyl cation is proposed. Co(II), Co(III) and Zn(II) complexes of pentane-2,4-dione react with alkyl halides precursors of stabilized carbenium ions, to give 3-alkylpentane-2,4-diones.

C-alkylation of β diketones with benzylpyridinium salts. Evidence for chain radical mechanisms

Abstract 1-(p-Substituted benzyl)-2,4,6-triphenylpyridinium cations react with β -diketone anions by mechanisms which depend on the para-substituent. The p-methoxybenzyl derivative undergoes S N 1 displacement yielding O- and C-benzylated products. The pnitrobenzyl compound reacts by a chain radicaloid mechanism and gives high yields of C-pnitrobenzylated diketones. The parent benzyl compound forms some C- and some O-benzylated products, together with bibenzyl, probably by a radical chain reaction which was suppressed by radical traps.

Reactions of copper(II) β-diketonates under free radical conditions. Preparation of highly congested β-diketones.

Abstract Copper(II) β-diketonates react with alkyl bromides under free radical conditions to give highly congested β-diketones such as 3-(1-adamantyl)-3-alkylpentane-2,4-diones. Another typical free radical reagent: benzoyl peroxide, reacts also functionalizing the intercarbonyl positions.

Cobalt(II) chloride bistriphenylphosphine catalyzed alkylations of β-dicarbonyl compounds

Abstract The alkylation of β-dicarbonyl compounds with several benzyl halides in chloroform and in the presence of potassium carbonate is accelerated by the presence of cobalt(II) chloride bistriphenylphosphine, thus broadening the scope of this alkylation method.

Reactions of copper(II) β-diketonates under free radical conditions. II. Diazonium salts as aryl radicals source in the arylation of β-diketones

Abstract Copper complexes of 2,2,6,6-tetramethylheptane-3,5-dione and other β-diketones afford α-aryl-β-diketones when treated with arenediazonium tetrafluoroborates and copper powder in dichloromethane

Preparation and conformational analysis of severely hindered β-diketones. Dipole moment determinations and theoretical calculations.

Abstract Several β-diketones bearing bulky substituents at the intercarbonyl positions have been prepared by alkylation of the cobalt(II) complexes of the unsubstituted diketones. Agreement between experimental and calculated dipole moments is fairly good thus rendering Molecular Mechanics a safe tool for the conformational analysis of the title molecules. The most populated conformations have been evaluated for nine ϱ-diketones bearing 1- and 2- adamantyl, tert -butyl, cyclohexyl, 1-phenylethyl and benzhydryl groups as well as two methyl groups and one methyl plus one 1-adamantyl groups.